1. Field of the Invention
This invention relates generally to navigation systems and more particularly to a system which uses a locally generated coordinate frame for determining the position of a platform relative to a plurality of other platforms operating within a common spatial reference system.
2. Description of Related Art
Current navigation/location systems both military and civilian, rely heavily on GPS satellite signals as the basis for locating entities in an earth reference frame. The currently used global positioning system (GPS) consists of 24 globally dispersed satellites which enables a user to obtain his position and velocity in space by sensing coded signals from a predetermined number, typically four, of viewable satellites. This system, moreover, is well documented and reference, if need be, can be made to U.S. Pat. No. 4,114,155 entitled xe2x80x9cPosition Determining Apparatus And Methodxe2x80x9d or to a publication entitled Understanding GPS: Principles and Applications, Elliot D. Caplan, Artech House, Boston, 1996.
However, there are growing concerns over GPS vulnerability to jamming and reduced reliability of operation when the communication path to available satellites are blocked by terrain or buildings. The basis for these concerns regarding military systems is manifestly obvious. However, these concerns also apply to civilian systems. For example, GPS is not employed as an aid to civilian aircraft landing systems because of its implicit vulnerability to jamming by a terrorist or some other entity. Similarly, a concern regarding the potential denial of GPS by terrain or buildings is the same for civilian and military applications. Accordingly, a new system approach is needed that provides not only a backup navigation/location capability under the conditions where GPS signals are not available, but also one which can operate entirely independently of a satellite navigation system such as GPS.
It is an object of the present invention, therefore, to provide a system for generating extremely high accurate positional information of a sensor platform.
It is another object of the invention to provide a system for generating highly accurate position information regarding the relative location of a plurality of sensor platforms within a spatial reference system.
It is yet another object of the invention to provide a system which provides three dimensional location of a plurality of sensor platforms within a local area coordinate frame using directive beams.
It is still another object of the present invention to provide a highly accurate local area positioning system which can operate without reliance on external systems such as a satellite navigation system.
These and other objects are achieved by a local area positioning system (LAPS) which utilizes networking as an expedient to enhancing capabilities associated within a given platform, also referred to as a node, in a system which includes a plurality of platforms consisting of airborne and/or ground base vehicles that are coupled via a platform-to-platform local area network. The system is similar to GPS in that ranging is employed as a basis for locating the various platforms; however, the system of the subject invention differs from GPS in two respects: (1) the platforms themselves establish a spatial reference system for location; and, (2) communication between platforms is accomplished using directive millimeter wave beams, and where measurements and communicated estimates of node locations, in a local inertial reference frame, are processed via Kalman tracking filters to generate updated estimates of position and velocity vectors associated with each node.
Further scope of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood, however, that the detailed description and specific example, while disclosing the preferred embodiment of the invention, is given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the following detailed description.